I've called them many times and can't get through. Also requested call back but they don't call.
I'd start the process with your card provider but keep trying to get in touch via the phone with Amazon, even if it's just a call back request every couple of days.
Unfortunate as I've never had anything but stellar service from Amazon CS when I've needed it, it's one of the reasons I use the platform as extensively as I do if I'm honest. Hopefully your case is just a hiccup due to current events bud, sucks for you though and I do hope you get things sorted out.
Amazon aren't calling back? I called them a couple of days ago, it was instant.
This is my experience, I've even asked for them to contact me on the phone via their internet support forms and I've been connected within minutes. The people you speak with generally bend over backwards, albeit with a little pushing at times to get the most out of them depending on the issue.